1. Field of the Invention
The present invention relates to a plasma processing apparatus which generates plasma within a vacuum chamber to process semiconductor substrates using the plasma.
2. Description of the Related Art
Generally, as an apparatus for manufacturing semiconductor devices, liquid crystal displays, and the like, a plasma processing apparatus has been used to process a surface of a substrate using plasma. For example, the plasma processing apparatus includes a plasma etching apparatus for etching the substrate, a plasma chemical vapor deposition (CVD) apparatus for performing a CVD process on the substrate, and the like.
As shown in FIG. 1, such a plasma processing apparatus 1 comprises two planar electrodes 10 and 20 equipped in parallel to each other at upper and lower portions of chamber 14. A substrate S is mounted on the lower electrode 20. Thus, the lower electrode 20 is also referred to as a substrate mounting table. The upper electrode 10 is located opposite to the lower electrode 20. The upper electrode 10 is provided with an electrode plate 12 which has a plurality of gas orifices, and the electrode plate 12 is referred to as a shower head 14. The upper electrode 10 is connected to a process gas source. When performing a process, the process gas is supplied to a space between the two electrodes 10 and 20 through the gas orifices of the electrode plate 12. The process gas supplied to the space between the electrodes is converted into plasma by application of RF power to the electrodes, and the surface of the substrate is process by the plasma.
The plasma processing apparatus 1 is provided with an air discharge unit (not shown) to discharge gas therein to the outside. The air discharge unit is connected to a pump (not shown) located at the outside of the plasma processing apparatus 1 to suck and remove the gas in the plasma processing apparatus 1 and to maintain a vacuum in the plasma processing apparatus 1.
As shown in FIG. 1, such a plasma processing apparatus 1 comprises two planar electrodes 10 and 20 equipped in parallel to each other at upper and lower portions of chamber 14. A substrate S is mounted on the lower electrode 20. Thus, the lower electrode 20 is also referred to as a substrate mounting table. The upper electrode 10 is located opposite to the lower electrode 20. The upper electrode 10 is provided with an electrode plate 12 which has a plurality of gas orifices, and the electrode plate 12 is referred to as a shower head.
The outer lifting bar 40 is separately provided at the outside of the lower electrode 20. That is, the outer lifting bar 40 is provided in a space between a side surface of the lower electrode 20 and a wall of the plasma processing apparatus to move up and down.
The inner lifting pin 30 and the outer lifting bar 40 serve to convey the substrate into or out of the plasma processing apparatus. The operation of the inner lifting pin 30 and the outer lifting bar 40 will be briefly described as follows.
When conveying a substrate into the processing plasma processing apparatus from the outside, a conveying unit provided at the outside of the plasma processing apparatus enters the plasma processing apparatus. Then, the inner lifting pin 30 is raised to lift and support the substrate above the conveying unit. After the conveying unit is retracted from the plasma processing apparatus, the inner lifting pin 30 is lowered, and places the substrate on the lower electrode 20. In this state, a predetermined process is performed on the substrate using plasma.
After completing the process for the substrate, the inner lifting pin 30 is raised again to lift the substrate, and is stopped at a predetermined height. At the same time, the outer lifting bar 40 is also lifted, and a substrate supporting bar 44 is rotated towards the center of the lower electrode 20 and is located below the substrate at a lower height than that of the inner lifting pin 30. Then, as the substrate supporting bar 44 is raised, the substrate is lifted above the inner lifting pin 30 by the substrate supporting bar 44.
The inner lifting pin 30 is lowered again, and a new substrate is conveyed into the plasma processing apparatus by the conveying unit from the outside. Then, the inner lifting pin 30 is raised again to lift and support the new substrate. After the conveying unit is retracted from the plasma processing apparatus, the inner lifting pin 30 is lowered, and places the substrate on the lower electrode 20. Additionally, when the conveying unit enters the plasma processing apparatus again, the substrate supporting bar 44 is lowered, and transfers the processed substrate to the conveying unit. When the conveying unit is retracted from the plasma processing apparatus, the processed substrate is also conveyed out of the processing apparatus.
In FIG. 2, the conventional outer lifting bar 40 serving to convey the substrate as described above comprises an upper cover 42, the substrate supporting bar 44, and a case 46. The upper cover 42 is located above the substrate supporting bar 44. As a result, while the substrate supporting bar 44 is operated, the upper cover 42 is lowered to a side of the lower electrode 20, and prevents the plasma from attacking an upper surface of the substrate supporting bar 44 and damaging the substrate supporting bar 44. The substrate supporting bar 44 is raised above the lower electrode 20, and is then rotated towards the center of the lower electrode 20 to support the substrate. The case 46 is lowered during the process, and defines a space to receive the substrate supporting bar 44. The case 46 is tightly coupled with the upper cover 42 to prevent the plasma from attacking the side surface of the substrate supporting bar 44. However, since the case has a complicated structure, there are problems of increasing manufacturing costs while complicating maintenance of the plasma processing apparatus. Additionally, when the outer lifting bar 40 is driven, there is a possibility of collision between the upper cover and the case. Meanwhile, in addition to the outer lifting bar 40, a baffle 50 is provided to the side of the lower electrode 20 to control the flow of plasma. Thus, there are difficulties in manufacturing of the baffle 50, as such a recess must be formed on the baffle 50 to allow the case 46 to move through the recess as shown in FIG. 2, and in coupling of the case 46 to the baffle 50. Additionally, various particles can be accumulated in a gap between the baffle 50 and the case 46, causing process errors.